1. Field
The present disclosure relates generally to communication systems, and more particularly, to a programmable frequency divider for local oscillator generation.
2. Background
A wireless device (e.g., a cellular phone or a smartphone) may transmit and receive data for two-way communication with a wireless communication system. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a transmit local oscillator (LO) signal with data to obtain a modulated radio frequency (RF) signal, amplify the modulated RF signal to obtain an output RF signal having the desired output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna, amplify and downconvert the received RF signal with a receive LO signal, and process the downconverted signal to recover data sent by the base station.
The wireless device may include one or more oscillators to generate one or more oscillator signals at one or more desired frequencies. The oscillator signal(s) may be used to generate the transmit LO signal for the transmitter and the receive LO signal for the receiver. The oscillator(s) may be required to generate the oscillator signal(s) to meet the requirements of the wireless communication system with which the wireless device communicates.
Frequency dividers are used extensively for generating LO signals. Typically, frequency dividers only provide a fixed division ratio. Accordingly, multiple frequency dividers are typically needed in multi-band transceivers. Existing programmable frequency dividers do not meet the stringent LO requirements (e.g., small chip area, good phase noise requirement, quadrature output) in cellular transceivers. Accordingly, there is a need for a programmable frequency divider for generating LO signals in multi-band cellular transceivers.